11-(4-[2-(2-hydroxyethoxy)ethyl]-1-piperazinyl]dibenzo[b,f]-1,4-thiazepine (I) is a well established drug substance known under the INN name quetiapine.

It is used as hemifumarate salt as an antipsychotic or neuroleptic.
Several methods for the preparation of quetiapine are known, as disclosed in e.g. GB 8607684, GB 8705574, and WO 01/55125. The known methods include reacting a halo derivative (e.g. iminochloride) of dibenzo[b,f][1,4]-thiazepin-11(10-H)-one with 1-(hydroxyethoxyethyl)piperazine; reacting the aforementioned halo derivative with piperazine and reacting the resulting intermediate with a halo ethoxyethanol; and reacting a haloethylpiperazinylthiazepine derivative with ethylene glycol.